Economics continued

The earliest method for manufacturiag carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally heated retorts. Safety concerns, short Hves of the retorts, and low production capacities led to the development of an electric furnace process, also based on reaction of sulfur and charcoal. The commercial use of hydrocarbons as the source of carbon was developed in the 1950s, and it was still the predominate process worldwide in 1991. That route, using methane and sulfur as the feedstock, provides high capacity in an economical, continuous unit. Retort and electric furnace processes are stiU used in locations where methane is unavailable or where small plants are economically viable, for example in certain parts of Africa, China, India, Russia, Eastern Europe, South America, and the Middle East. Other technologies for synthesis of carbon disulfide have been advocated, but none has reached commercial significance. 

Natural circulation evaporators like those shown on Figure 8.16 may be equipped for continuous salt removal and thus adapted to crystallization service. For large production rates, however, forced circulation types such as the DTB crystallizer of Figure 16.10(g), with some control of crystal size, are the most often used. The lower limit for economic continuous operation is l-4tons/day of crystals, and the upper limit in a single vessel is 100-300 tons/day, but units in parallel can be used for unlimited capacity. 

Figure 7 shows a schematic diagram of the model calciner used for studying an economic continuous two-stage calcining system. The exhaust gas from first stage kiln is fed as fuel for second stage kiln. 

Economics. Continuous processes are usually cheaper for large volume production. Batch processes are usually cheaper for specialty polymers. 

Within a few years, Dow replaced the can process with the more economical continuous hulk polymerization process still used today. Generally, the key problems associated with manufacture of the polymer are removal of the heat... 

Whereas nylon 66 manufacture requires a pressure polymerization step, nylon 6 can easily be polymerized at atmospheric pressure in the presence of initiators. An economic, continuous process in which these conditions were applied was developed by H. Ludewig [24] at Berlin in 1940, the so-called VK process (Fig. 4). The initials VK stand for "simplified continuous" from the German "vereinfacht kontinuierlich". 

Fineness (down to 1 denier), and cooling and stretching uniformity are easy to obtain, so that uniformity in the physical and mechanical properties (tenacity, elongation, dyeability, etc.) is guaranteed. All in all, the process represents an economical continuous method of obtaining finer PP filaments. 

One of those key implications is the need to focus upon the necessary linkages between social, economic and organisational factors in the analysis of the origins and processes of technological innovation. Mainstream neo-classical economics continues to focus excessive attention only upon either market demand as puUing ... 

Optimization of the balance of physical and mechanical properties including scratch resistance, stiffness, low temperature impact, dimensional stability, processability, surface aesthetics, durability and economics continues to be a driving force for development. Often the most demanding properties to improve for TPOs today are scratch resistance and low temperature impact strength. Traditionally, enhanced low temperature impact resistance has come from rubber toughening by increasing the elastomer component. However, with an increase in elastomer content a reduction in the scratch resistance performance can often occur. This reduction in scratch resistance is attributed to a decrease in the TPO rigidity,... 

---